San Diego Scientists Help Develop New Twist On In Vitro Fertilization

"This method could help parents who want to have their own child disease-free," said a Salk Institute scientist who co-led the study.

A team of researchers including scientists from San Diego have developed a new approach to in vitro fertilization that combines components from the eggs of two different women. They say if follow-up studies prove successful, it could one day improve treatments for infertility or help prevent devastating diseases.

But some experts are concerned that this and similar approaches, which have already reportedly been used in a number of human births, have not yet been proven safe.

The new technique involves extracting tiny cells called polar bodies from the egg of a woman who may be struggling with infertility or may be at risk of passing down mitochondrial disease to her children. Polar bodies normally play no role in fertilization, but they can when they're implanted into a healthier egg from a donor.

In a new study published Thursday in Cell Stem Cell, researchers co-led by the Salk Institute's Joseph Ecker show that when this hybrid egg is fertilized, it can give rise to cells that appear capable of becoming viable human embryos. These embryos could contain DNA from women who would otherwise struggle to have healthy kids of their own.

"It's going to need more than a few experiments, but I think it's very promising," Ecker said. "I would say this method could help parents who want to have their own child disease-free. It's really just one additional advance over IVF."

But any baby created this way would carry a small amount of DNA from the donor. Mitochondria — cellular "batteries" that contain their own DNA — would be passed down from the donor to the baby. That could help prevent heritable mitochondrial diseases, but it would also lead to what some have called "three-parent" babies.

Ecker said this new approach would essentially improve the odds of so-called "three-parent" IVF actually working in the clinic. He said including the woman's extracted polar bodies would give the hybrid egg multiple chances of becoming a viable embryo during the in vitro fertilization process.

"You could have two attempts from the same egg, where you move both the nucleus and the polar body into a donor egg," Ecker said.

UC Davis's Paul Knoepfler, who was not involved in the study, said the results convincingly show this new method can create human embryonic stem cells. But he said the study doesn't yet prove this would be a safe approach for creating healthy human children.

"It seems premature to discuss the potential future use any time soon of (this) technology as, for instance, an approach to infertility or mitochondrial disease prevention," Knoepfler wrote in an email to KPBS.

Regulators in the U.K. have already decided to approve moving forward with "three-parent" IVF techniques. Ecker said in the United States, additional animal studies are planned to test the safety of these approaches before the FDA would consider approval.